At the present, there is a high demand to manage environmetally harmful waste in general, and in particular fly ash from combustion of waste and fluorescent tubes. Combustion of e.g. house refuse results in residual materials such as slag and fly ash which contain mercury and heavy metals, such as barium, cadmium, cobolt and chrome, in addition to large quantities of mercury and lead. These materials are considered as hazardous waste in Norway and in the most of the European countries. During the destruction of fluorescent tubes, the powdery fluorescent material therein is separated from the metal, plastic and glass components including mercury. This powder, comprising about 38-40 different elements, is also characterized as hazardous waste in most of the European countries. At the present there is no satisfactory or environmetally safe method to handle such waste, and one has to resort to deposits in special waste storage.
NO Patent 172103 describes a method for treating waste material. According to this process, solid and/or liquid waste is/are combined with a binder material, in this case clay, whereupon the granulated/powdery mixture is subjected to pyrolysis to remove volatile components in the waste. The waste is then fed to a furnace at oxidizing conditions to oxidize remaining volatile components and at least some of the bound carbon, whereupon the waste is passed through a vitrification process to form a solid aggregate.
However, the above process is different from the present in several ways, as the heat treatment is applied to the waste in its solid form. The resultant aggregate will be at least partly porous as a result of the stripping of volatile compounds and carbon. This will allow for water penetration which will result in leaching of environmetally hazardous compounds and elements. The waste treated in accordance with the method of NO Patent 172103 can for that reason not be stored on e.g. waste disposal sites or recovered as recyclable raw materials or products because of the risk of releasing environmetally hazardous components from e.g. water draining from waste disposal sites.